For weeks leading up to Tuesday's season-five summer finale, ABC Family has reminded viewers just how fatal the episode will be with the "#fAtalfinale" hashtag with the death of a character. As executive producer Marlene King tells The Hollywood Reporter,the death has been in the works for more than a year — "It's been a very well-thought plan," she reassures. "It wasn't like 'spin the dial and see who gets killed.' "

The episode — described by King as "thrilling, sad and shocking" — starts off on Thanksgiving Day, before flashing back to 36 hours earlier. With "a hint of the holidays coming up," King says the summer finale, titled "Taking This One to the Grave," layers in big clues for the Christmas episode airing later this year.

"Maybe more than any other [finale], this one takes the show in a very unexpected direction. There is a dark turn and it's a surprising turn," King teases. "I have goosebumps even telling you this — fans are going to be left speechless. I think it's one of those where, even people here who have seen the episode who work on the show, their jaws hit the floor. Tissue boxes were out; people were crying."

King shares six clues to look for in the summer finale and the second half of the season.

The Liars versus Alison: Trust between Alison and the four Liars — Aria, Spencer, Hanna and Emily — is at an all-time low when the summer closer kicks off. "The Pretty Little Liars have all cut off Ali. There's a line in the finale where somebody says, 'If she can't play with her dolls, maybe she's ready to end the game, Alison.' That's where we start the finale," King hints. "The Liars have always asked since the beginning of the show, 'Why did she pick us? Why me?' They come up with a very good answer to that question in this finale. It really answers a lot of emotional questions that the Liars have been asking since the pilot."

One step forward for Ezra and Aria: Will "Ezria" be back on good footing by the end of the summer finale? "There's a really fun Ezra and Aria scene in the finale, I'll say that," King teases. "It's not all sadness and despair. There are a couple of very romantic scenes as well."

Is Alison really "A"? Over the past several weeks, speculation over the identity of "A" has focused on Alison. Naturally, King keeps mum when asked if there was reason to believe the Alison-"A" connection: "I can't tell you the answer to that!" she says with a laugh.

A vulnerable Mona: Was Mona's heart-to-heart with Aria an act or is she turning over a new leaf? "I don't think it's an act at all," King says of the emotional moment last week. "Even if you're a villain in this show, you're a three-dimensional villain. Mona's a real person and she became who she was because of the way Alison treated her. She snapped. I loved showing that side of her and even on her worst day, I loved seeing Alison's vulnerability as well."

"Emison" factor: "Since we revealed Alison was alive, the 'Emison' fans have been outspoken. A bulk of the audience really embraces that couple," King says. "I wasn't surprised by how vocal and how many of those shippers there are." Emily and Alison's dynamic is "one of the most emotionally complex relationships in the show," she adds, "on a friendship level and possibly on more than a friendship level." Though silent about any significant movement on the "Emison" front, she promises: "There is so much going on between them and we continue to explore that dynamic."

Mrs. D's killer: The question of Mrs. DiLaurentis' killer will be one of the main mysteries next year. "It's a longer mystery. I think that's season six," King says.